Though Olbermann eventually had similar exits from cable news as from his first run at ESPN (and none of this is to imply that management was entirely blameless along the way), he achieved a great deal more success at MSNBC, where he was instrumental in establishing an identity for the fledgling network, than Cosell ever did occupationally outside of sports. Whether Cosell would have had greater accomplishment in other realms today because he or the times would have been different, or a combination thereof, is a matter of interpretation.
Vitamin D (cholecalciferol) is normally synthesized in the skin under the influence of sunlight in a nonenzymatic manner. In addition, vitamin D (ergocalciferol) may be ingested from fish or plant sources. Vitamin D is then hydroxylated in the liver to 25-hydroxyvitamin D (calcidiol, 25[OH]D), which is the major circulating form of vitamin D and the best index of vitamin D sufficiency. Calcidiol is hydroxylated primarily in the kidney to 1,25-dihydroxyvitamin D (calcitriol), which is the most active form ( figure 1 ). 1,25-dihydroxyvitamin D is also formed in some other tissues but is used only within those tissues and not circulated. (See "Overview of vitamin D", section on 'Metabolism' .)
Combined pituitary hormone deficiency (including ACTH deficiency) due to genetic pituitary abnormalities is rare. ACTH and cortisol deficiency have been described in patients with multiple pituitary hormone deficiencies due to mutations in the PROP-1 (Prophet of Pit-1) gene, even though PROP-1 is not expressed in corticotropes. The onset of cortisol deficiency, which may be severe, ranges from childhood to late adulthood [ 2-5 ]. Mutations in other transcription factors involved in early pituitary development (HESX1, LHX4) also can result in variable degrees of hypopituitarism that include ACTH deficiency [ 6,7 ]. (See "Causes of hypopituitarism", section on 'Genetic diseases' .)